Update Functions/Node dockerfile to provide Azurite by default (#1566)

Necessary for local development.

Author: diberry

containers/azure-functions-node/.devcontainer/Dockerfile

@@ -8,3 +8,9 @@ FROM mcr.microsoft.com/azure-functions/node:4-node${VARIANT}-core-tools
 # RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
 #     && apt-get -y install --no-install-recommends <your-package-list-here>
 
+# [Optional] Uncomment if you want to run your Function locally with 
+# local.settings.json using `"AzureWebJobsStorage": "UseDevelopmentStorage=true"`
+# RUN sudo -u node npm install -g azurite
+
+# [Optional] Uncomment if you want to install more global node packages
+# RUN sudo -u node npm install -g <your-package-list-here>